The present invention relates to a device for transferring a load by thrust and traction in the same plane, called the transfer plane, this device being used in particular to transfer a tool a mold, or a metal mass, from a moving support onto a stationary support, said device being designed to be mounted either on the moving support or on a stationary support, this device comprising at least one hinged handling arm designed to move in the same plane, called the hinge plane, this hinge plane being substantially perpendicular to the load transfer plane, this an comprising at least one front member and one rear member, the rear member being coupled to said support by at least one first hinge, the front member being coupled on the one band to the rear member by at least one second hinge and on the other hand to said load by hooking means provided at its free end, both hinges being located in said hinged arm's hinge plane, this device also comprising driving means designed to move said arm between two end positions, a first folded up position in which tie arm is retracted between the load and the support, and a second fully unfolded position in which the an is extended between the load and the support and reciprocally.
In industry, lift trucks or stackers are commonly used to handle big loads. More specifically, in the field of machine tools or presses used for clicking and forming sheet metal or any other material the tool change is performed by lift trucks which are equipped with a transfer device working by thrust and traction in the same plane. In order to transfer the tool from the lift truck's tray or forks onto the table or the tray of a machine-tool or a press, and reciprocally, known transfer devices making it possible to push and pull the load are installed between the tool and the sliding push plate on the truck's mast. These transfer devices generally comprise a direct double thrust action jack, a multiplier scissors system or chains working by thrust and traction. Nevertheless, these devices all present the drawback of being bulky, particularly in the transfer direction, which moves the load away from said truck's mast. The result of the load being moved away is that its center of gravity is removed in relation to the truck's center of gravity.
The effects of this removal are as follows: it is necessary to oversize the truck's tray and forks, the truck's maneuverability is reduced and the driving wheel's adherence is reduced. It is important to specify that the capacities of a handling device such as a lift truck, are given by the value of the maximum transportable load and the removal of the center of gravity of tie load being transported in relation to the mast's axis. The assembly of the above-mentioned transfer devices therefore presents the drawback of heavily penalizing handling devices' rated capacities, which can be estimated in the region of 25 to 35%.
Some transfer devices have been designed to try and overcome these problems by using a hinged thrust and traction arm in the same plane. In the publication US-A-2 672 249, the arm is comprised of two distinct parts moved by a central jack which drives vertical racks engaging with toothed sectors provided at the corresponding end of both pants of the arm. This drive system is relatively bulky, it is not retractable into the thickness of the mast and requires having two supporting points on either side of the am a first one on the mast side and a second one on the load side. The system for hooking the load at the end of the arm is complex and not very quick to implement. In the publication DE-A-17 81 367, the arm is controlled by a jack, the body of which is securely fixed to the truck, the rod is securely fixed to the front part of the arm and the arm is doubled by additional hinged rods to guide its movements. Despite seeming simpler than the previous one, this drive system presents more or less the same drawbacks.